Silphium mohrii

Silphium mohrii, known by the common names Mohr's rosinweed^[2] and shaggy rosinweed, is a species of flowering plant in the family Asteraceae. It is native to the Southeastern United States, where it is native only to northern Alabama, southern Tennessee, and extreme northwest Georgia.^[3][4] It occurs in prairie remnants and rocky limestone openings, often in open, dry habitats with thin soils. Because of its restricted range and severely declined habitat, it is considered a vulnerable species.

It produces heads of yellow flowers in late summer, typically flowering from August to September.^[5]

The species was first described by John Kunkel Small in 1897.^[4]

Silphium mohrii is a tall perennial distinguished by its densely shaggy-hirsute stems, inflorescence, and phyllaries, with hairs often exceeding 5 mm in length. The inflorescence is typically corymbose, bearing multiple flower heads (generally 3–15).^[5]

It is most similar to other Silphium species with non-pinnatifid leaves, but can be distinguished by its long, shaggy pubescence and multi-headed inflorescence.^[5]

The species was first described by John Kunkel Small in 1897. In a 1999 revision of Silphium, Jennifer Ann Clevinger treated S. mohrii within Silphium sect. Silphium, a group characterized by fibrous roots and caulescent growth.^[6]